Unitary joint-forming structure



Aug. 12, 1969 R. J. GRENZEBAC'K 3,460,447

UNITARY JOINT-FORMING STRUCTURE Filed June 2o, 1967 MN 24) l 22) 4o FIGAgg ed 5e' ATTORNEYS aired States Patent t 3,460,447 UNITARY.IOIN'B-IFGRMING STRUCTURE Robert J. Grenzeback, 16 Mason St.,Winchester, Mass. 01890 Filed .lune 2%, 1967, Ser. No. 647,353 Int. Cl.Eii1c 1.1/10, 1]/12 U.S. Cl. 941-18 5 Claims ABSTRACT OF THE IHSCLOSUREBACKGROUND OF THE INVENTION In the construction of roads, bridges, andother types of structures in which a viscous hardenable material such asconcrete, asphalt, or the like is poured within forms and allowed toset, it is often desirable to provide expansion joints between adjacentsections of the construction in order to allow for expansion andcontraction of the sections due to variations in load and atmosphericconditions. These expansion joints are generally of relatively smalldimensions (often of the order of fractions of an inch) and thereforecannot readily be formed by the usual technique of inserting a standardwooden form between the adjacent sections while pouring them andsubsequently removing the form, since the small spacing severelyrestricts access to the form which tightly adheres to both sectionsafter they have set. On the other hand, the form, being relativelyincompressible, cannot permanently be left in place since this wouldprevent the necessary expansion and contraction of the sections relativeto each other.

Present construction techniques utilize what is known as a hopscotchmethod of construction to solve the problem of forming expansion joints.In this method, alternate construction sections are poured within woodenforms erected for this purpose, the sections are allowed to set, and theforms are then removed; spacing elements such as slabs of cork are nextpositioned adjacent the hardened sections and the sections which havebeen skipped over are then poured. The cork slabs may then be left inplace if it is desired to form an expansion joint of the type having apartially limited expansion capability (cork being a material which maybe classified as partially compressible) or may be chipped out by handand the joint lled with sealant if it is desired to form a joint havinga greater expansion capability. Such techniques are quite timeconsuming, and unduly lengthen the time spent in construction. Further,in cases in which sealant is to be introduced into open-bottom joints ofthe type found in bridges and similar structures, special preparationsfor retaining the sealant must be made and these preparations oftenfurther lengthen the construction time. It is therefore desirable that amore efficient and more economical method of constructing expansionjoints be found.

SUMMARY OF THE INVENTION I have found that expansion joints instructures formed from viscous hardenable materials may readily beformed SAAl? through the utilization of a simple yet elicient unitaryjoint-forming structure consisting of a core member, preferably of corkor of a foamed, closed celled, polystyrene plastic, and a pair of wallmembers which are attached to the core member on opposite sides of thecore to form a modular sandwich The wall members, which mayadvantageously be formed from a light Weight, relatively strong,non-corroding material such as ber glass, may be reinforced with anumber of stress-carrying rods which provide additional rigidity to theunitary structure and which can subsequently serve as attaching membersfor lirmly bonding the walls to the opposite sides of the expansionjoint which is being formed. The core member may, if desired, be removedafter the expansion joint has been formed; the wall members, on theother hand, which isolate the core member from the adhesive viscousmaterial, are permanently bonded to opposing sections of the joint. Aretaining lip for sealant-retaining gaskets may be directly incorporatedinto structures made in accordance with my invention to provide a `rapidmeans of forming sealant-retaining joints. Such structures as theseallow the formation of poured sections sequentially as well assimultaneously and thus greatly reduce construction time.

Accordingly, it is an object of my invention to provide a unitaryjoint-forming structure. Further, it is an object of my invention toprovide a unitary joint-forming structure which is simple and economicalto make and which may be left in place, or which may be partiallyremoved, after the joint has been formed. Yet a further object of myinvention is to provide a unitary joint-forming structure in which aretaining lip for sealant-retaining gaskets is formed directly. Still afurther object of my invention is to provide a unitary joint-formingstr-ucture which allows the pouring of adjacent sections in sequence.

`One feature of my invention resides in the provision of a pair ofrelatively thin non-corroding wall members surrounding a central core,the walls being adapted to remain in place after the sections have beenformed. Another feature of my invention resides in the provision ofstiifening bars attached to the wall members and spaced from the membersto provide increased resistance to buckling of the walls during thepouring or section-forming operation. Still another feature of myinvention resides in the provision of either a partially or a fullycompressible central core which is isolated from the poured sections bythe wall members and which provides both stiffening and spacing betweenthe sections during the pouring operation. A further feature of myinvention resides in the provision of a removable core member whichprovides rigidity to the structure during pouring but which is readilyremovable after the sections have been formed.

SPECIFICATION The above and other and further objects and features of myinvention will become more readily apparent when considered inconnection with the following detailed description of the drawings inwhich:

FIG. l is a pictoral View of a preferred form of unitary joint-formingstructure constructed in accordance with my invention, the structureshown being especially adapted to form expansion joints of the fullyexpanding type;

FIG. 2 is an end sectional view of the structure of FIG. 1 shownpositioned between adjacent sections to form an expansion joint, one ofthe sections being fully poured and the other only partially so;

FIG. 3 is an end sectional View of the structure of FIG. 2 showing thecore member partially removed and replaced with a sealing gasketsupporting a layer of sealing compound after the poured sections havehardened; and

FIG. 4 is an end sectional view of an alternative form of unitaryjoint-forming structure shown positioned between adjacent pouredsections, the structure shown being especially adapted to form expansionjoints of the partiallyexpanding type.

In FIG. 1, a unitary joint-forming structure constructed in accordancewith my invention comprises a core member 12 which is preferably formedfrom a foamed, closed-celled, polystyrene material attached on oppositefaces to walls 14 and 16. The latter may advantageously be formed from alight-weight, non-corrodable material such as fiberglass which may beformed in relatively thin but strong sections. As may be seen from FIGS.1 and 2 of the drawing, the wall 14- comprises a first relatively flatsection 18 having a flange 20 positioned adjacent the upper portion andextending substantially at right angles to the wall. An inwardlyextending wall section 22 connects the outer portion of the flange to asecond at wall section 24. The flange and the inwardly extending wallsection form a triangle extending outwardly of the structure forpurposes which will subsequently be described. A line of weakening 25may be formed in the upper portion of the core member 12. An angled wallsection 26 terminating in a horizontal flange 2S is provided at thebottom of the wall 14 to provide a footing for the structure. The wall16 is constructed similar to the Wall 14 and need not be described indetail.

A number of standoffs 30 are positioned along the Walls 14 and 16 andare secured to these walls by adhesive or the like. In the embodimentshown in the drawings, the standoffs are secured to the walls by meansof strands of fiber glass-reinforced plastic material which are bondedto the walls and which are subsequently allowed to set. Reinforcing bars32 are spot-welded to the standoifs 30 and act as longitudinalstiifening elements to prevent buckling of the walls 14 and 16.

The dimensions of the structure of my invention will depend on thedesired dimensions of the expansion joint and on the materials beingutilized. For typical expansion joints in concrete bridge structures andthe like, a closed celled, polystyrene core 11/2 inches thick and 14inches high is appropriate; the width of the core is, of course,dependent on the width of the bridge section. The walls 14 and 16 may beformed from a single 11/2 ounce mat of iiber glass with resin bonding;additional layers may be used as reinforcement if desired.

FIG. 2 of the drawings shows the structure 10 positioned intermediateadjacent sections of Vicous hardenable material which are being pouredto form a solid structure on hardening; for purposes of illustration,this material is shown as being concrete. At the stage illustrated inFIG. 2, one section 34 has already been fully poured, while anothersection 36 is still in the process of being poured. The structure 10serves as an end closure wall for the sections 34 and 36 during thepouring and hardening operation.

Ideally, the left and right hand sections on opposite sides of thestructure are poured at an equal rate so that counter-balancing forcesin opposite directions are applied to the structure 10. Under theseconditions, the core member 12 compresses slightly due to the appliedlforces. In practice, however, it is desirable to pour the sections 34and 36 serially, the pouring of the section 34 being completed beforethe poring of the section 36 is begun. This introduces a large force onthe right hand wall which would cause this wall to buckle outwardly(toward the left in this case) were it not for the strength introducedin my structure by the modular sandwich construction and by thestiffening elements 32 which resist any bending moment causing the Wallto buckle.

After the sections 34 and 36 have been formed and hardened, they arespaced a xed distance apart by the core member 12 and the walls 14 and16. The latter are Ltirmly bonded to the opposite sections 34 and 36when these sections harden and serve as end faces for the respectivesections; the core member 12 is then no longer needed to space the wallmembers and accordingly may be removed if desired. This may beaccomplished in any of several ways` Thus, the upper portion only of thecore member may be removed by separating it along the line of weakening25. This allows the introduction of sealant material in the upperportion as is described more fully below. Further, it may be chipped outby hand if made from a brittle, easily breakable material. Note in thisconnection that the core is isolated from the poured sections by thewalls 14 and 16. If the core member 12 is constructed of a foamedpolystyrene material, it may readily be removed by treating it with asuitable solvent to dissolve the material. This treatment completelydissolves the core member and leaves a void space which serves as thedesired expansion joint between the sections 32 and 34. Alternatively,since the closed-celled polystyrene core is relatively highlycompressible, it may be left in place Without adverse consequences. Thisis in strong contrast to prior forms of wood or the like which had to beremoved to allow operation of the expansion joint.

When the member 12 is removed, it is often desirable to protect theexpansion joint from extraneous substances such as water which may seepinto the joint and cause subsequent damage on freezing, or from pebblesor other material which may become trapped in the joint and prevent itsexpansion. Accordingly, in FIG. 3, which is an end sectional view of thestructure of FIG. 2 showing both sections fully poured and hardened, theupper portion of the core member 12 is removed along the line ofweakening 25 and a gasket 38 is positioned on the flange 20 and adjacentthe inwardly sloping wall 22; the remaining portion of the compressiblepolystyrene core may be left in place. In practice, this gasket may beformed from a rectangular sheet of neoprene one-eight of an inch thickand 41/2 inches wide doubled back on itself to form a U-shaped closurefor the expansion joint as shown. A ller material such as an asphaltcompound 40 is then poured over the gasket 36 and allowed to set. Afterthe filling compound is hardened, it rises or falls slightly in theexpansion joint as the width of the joint decreases or increases inaccordance with the forces and environmental conditions operating on thesections 34 and 36. The gasket 38 deforms accordingly, with the resultthat the expansion joint is sealed and remains so under all conditions.

It will be noted that a portion of the core member 12 remains in thejoint after it has been formed; this core portion, being relativelystrongly compressible, does not limit the expansion and contraction ofthe joint in any way. If the vmaterial used in the core is polystyreneor the like, it will be found that the core member will fragment aftercontinued expansion and contraction of the joint and will eventuallydrop through the bottom of the joint if the latter is of the open-jointtype such as is used in bridge construction.

So far I have illustrated an expansion joint of the openjoint type suchas is used in bridges. In this type of joint, a strongly compressiblematerial is used to allow essentially unlimited joint expansion.

In some types of construction, such as that encountered in roadways orbridges, it is often desired to limit the range of expansion throughwhich an expansion joint is allowed to operate. In such cases, it isdesirable that material such as cork, which is only partiallycompressible, be utilized in the expansion joint to provide thenecessary limiting action, the cork remaining in the joint after thesections are formed. In joints of this type, the desired sealantmaterial may be spread directly on the core member, since this member isto remain in place at all times. In this case, the sealing gasket may beomitted and the joint-forming structure may then be somewhat simplified.

An advantageous form of joint-forming structure for joints of thepartially expansible type is shown in FIG. 4 of the drawings. In thisiigure, a unitary joint-forming structure 42 is composed of a coremember 44 and a pair of wall members 46 and 48 respectively. Thestructure 42 is positioned intermediate adjacent construction sections50 and 52 which are being formed. As was the case with the structureI10, standots 54 and strengthening rods 56 are positioned on the wallsof the structure to provide additional resistance to buckling. Flanges58 and 60 are provided at the bottom of the walls 46 and 48 respectivelyto provide footing for the structure while the expansion joint is beingformed.

In contrast to the walls 14 and 16 of the structure 10, the walls 46 and48 of the structure 42 are relatively ilat and planar, and do not have aprojecting flange for receiving a sealing gasket. instead, a rathershallow strip 62 of wood or other material is attached to the coremember 44 between the walls 46 and 48 of the upper portion of thestructure. In FIG. 4, the attaching means are shown as being nails 64which are driven through the strip 48 into the core member 44; it willbe apparent, however, that other attaching means such as adhesive or thelike may also be utilized.

The strip 62 serves to maintain the spacing of the walls 46 and 48 whilethe sections 50 and 52 are hardening, and forms a narrow channel betweenthe walls for the reception of the sealant material when removed.Although the strong compressive forces acting on the walls of thestructure will pinch strip 62 to a certain extent, its removal is aidedby the fact this strip is of relatively shallow height and is thus morereadily removable from the structure than is a comparable strip ofgreater depth.

So far I have described how the structures of my invention may beutilized to form joints in such structures as bridges, roadways,culverts, etc. It will be apparent that my invention is not so limitedbut may be utilized to form joints in any structure in which sections ofa viscous, hardenable material are to be poured in sequence orSimultaneously with a gap between the sections to provide an expansionjoint. Further, it will be apparent that various changes may be made inthe structure of my invention without departing from the spirit andscope of my in vention. Thus, for example, the standoffs and reinforcingrods may be replaced by other reinforcing means such as small I-beamsections extending parallel to the wall with the web of the I-beamextending perpendicular to the wall. Further, core members other thancork or polystyrene may be used, the particular type of core membersselected being dependent on the compressibility of the core member andthe expansion characteristics desired `for the joint. Other changeswithin the scope and spirit of my invention may also be made, and it isintended that all the material described and shown herein be taken asillustrative only and not in a limiting sense.

Having described and illustrated a preferred embodiment of my invention,what I claim is new and desire to secure by Letters Patent is:

1. A joint-forming structure for separation during casting of adjacentsections of a hardenable material having, in combination:

a non-metallic core member appreciably more cornpressible than saidmaterial in the hardened state, said core member having walls adhesiveto said material in the hardened state,

a rod-like elongated metallic stitening member generally parallel to andspaced laterally from a wall of the core member and having its principaldimension along a line subjected to a bending moment by said castmaterial before hardening thereof,

a plurality of standois secured to said stiening member and spacing itlaterally from said wall to permit said material to surround itcompletely during casting, and

means to attach said standoffs rigidly to said Wall.

2. The combination according to claim 1, in which the last-mentionedmeans comprise flexibly conformable material covering portions of thestandofs and adhesively bonded to said wall.

3. The combination according to claim 1, in which the standofs aremetallic and the last-mentioned means are fibrous non-metallic strandscovering portions ofthe standois and adhesively bonded to said wall.

4. The combination according to claim 3, in which the standotfs arewelded to the stiffening member.

5. The combination according to claim 1, in which the core membercomprises a core appreciably more compressible than the hardenablematerial in the hardened state and wall members adhesive to saidmaterial in the hardened state.

References Cited UNITED STATES PATENTS 1,880,725 10/1932 Bleck 94-182,198,084 4/ 1940 Jacobson 94-18 2,301,137 1l/1942 Musall 94-182,352,314 6/1944 Fischer 94-18 2,540,251 2/ 1951 Fischer 94-18 2,967,4671/ 1961 Maude 94-18 3,060,817 10/1962 Daum 94-18 3,124,047 3/ 1964Graham 94-l8 3,234,860 2/1966i Laly 94-18 3,330,187 7/1967 Kohler 94--183,334,557 S/1967 Fitzgibbon 94-18 2,078,280 4/1937 Robertson 94-18 NILEC. BYERS, JR., Primary Examiner

